1. Field of the Invention
This invention relates to cutting tools and more particularly to a cutting tool with a removable insert.
2. Prior Art
It is common practice to provide cutting tools with a bit or tip of hard material, such as diamond, tungsten carbide, ceramic, or the like. The tip or bit is brazed or otherwise secured to the end of the tool shank or onto a replaceably mounted insert securable to a tool holder.
In manufacturing a typical cutting tool having a bit or tip of hard material, for example, a diamond-tip tool, a rough uncut diamond is set in a dop or metal slug with a brazing torch, and a rough lapping operation is performed. A fine-finish grinding or lapping operation is then performed and the diamond is again heated to remove it from the dop. It is then set in a tool shank or permanent holder with a solder (usually silver) by the application of heat, e.g., from a brazing torch. The tool shank is then either ground or placed on a belt sander to clean the excess flux and solder. Each of these steps subjects the tool and tip to substantial heat-induced stresses.
When a tool of the above type requires sharpening, the practice has been to remove the diamond, by the application of heat, for examination. The diamond is then mounted in a brass holder, by brazing, and the side contours are lapped. The diamond is then demounted from the brass holder by the application of heat and secured to a dop. It is either mechanically held in the dop or may be held in lead, which requires less heat than used in brazing. The cutting surface, sometimes called "the table" is then lapped. The diamond is again mounted in its permanent holder or tool shank, by brazing. The mounted diamond and holder are then cleaned to remove excess brazing compound, a step that involves substantial care to avoid damage to the diamond.
It will be apparent from the above that the typical procedures require skillful operations that are time consuming and, hence, expensive to perform, and subject the cutting tool and diamond tip to a great many heating steps, which are deleterious to the diamond or other tip material that may be used.
One approach that has been adopted, in an attempt to avoid some of the problems with tools of the aforementioned type, has been to mount bits in supports or inserts that are removable. Where the bit and insert are inexpensive, the insert and used bit can be discarded. Where the bit is expensive, the insert and bit can be removed as a unit and resharpened. The discarding of bits and inserts is of course wasteful and yet the resharpening of bits has not been satisfactory because of the need for accurate readjustment of the insert in the holder and/or readjustment of the holder in the machine tool after sharpening of the bit, to accommodate the change in the location of the cutting surface or edge. For example, the sharpening of bits or inserts of known cutting tools typically requires subsequent accurate adjustments, as by shimming or the like, to relocate the sharpened surface or table of the cutting bit in its critical location relative to the tool holder if the tool is to cut properly.